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Midlatitude daytime D region ionosphere variations measured from radio atmospherics

Publication ,  Journal Article
Han, F; Cummer, SA
Published in: Journal of Geophysical Research: Space Physics
January 1, 2010

We measured the midlatitude daytime ionospheric D region electron density profile height variations in July and August 2005 near Duke University by using radio atmospherics (or sferics for short), which are the high-power, broadband very low frequency (VLF) signals launched by lightning discharges. As expected, the measured daytime D region electron density profile heights showed temporal variations quantitatively correlated with solar zenith angle changes. In the midlatitude geographical regions near Duke University, the observed quiet time heights decreased from ∼80 km near sunrise to ∼71 km near noon when the solar zenith angle was minimum. The measured height quantitative dependence on the solar zenith angle was slightly different from the low-latitude measurement given in a previous work. We also observed unexpected spatial variations not linked to the solar zenith angle on some days, with 15% of days exhibiting regional differences larger than 0.5 km. In these 2 months, 14 days had sudden height drops caused by solar flare X-rays, with a minimum height of 63.4 km observed. The induced height change during a solar flare event was approximately proportional to the logarithm of the X-ray flux. In the long waveband (wavelength, 1-8 Å), an increase in flux by a factor of 10 resulted in 6.3 km decrease of the height at the flux peak time, nearly a perfect agreement with the previous measurement. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short, rather than the long, wavelength X-ray flux changes. © 2010 by the American Geophysical Union.

Duke Scholars

Published In

Journal of Geophysical Research: Space Physics

DOI

EISSN

2169-9402

Publication Date

January 1, 2010

Volume

115

Issue

10

Related Subject Headings

  • 5109 Space sciences
  • 5101 Astronomical sciences
  • 3706 Geophysics
  • 0401 Atmospheric Sciences
  • 0201 Astronomical and Space Sciences
 

Citation

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Han, F., & Cummer, S. A. (2010). Midlatitude daytime D region ionosphere variations measured from radio atmospherics. Journal of Geophysical Research: Space Physics, 115(10). https://doi.org/10.1029/2010JA015715
Han, F., and S. A. Cummer. “Midlatitude daytime D region ionosphere variations measured from radio atmospherics.” Journal of Geophysical Research: Space Physics 115, no. 10 (January 1, 2010). https://doi.org/10.1029/2010JA015715.
Han F, Cummer SA. Midlatitude daytime D region ionosphere variations measured from radio atmospherics. Journal of Geophysical Research: Space Physics. 2010 Jan 1;115(10).
Han, F., and S. A. Cummer. “Midlatitude daytime D region ionosphere variations measured from radio atmospherics.” Journal of Geophysical Research: Space Physics, vol. 115, no. 10, Jan. 2010. Scopus, doi:10.1029/2010JA015715.
Han F, Cummer SA. Midlatitude daytime D region ionosphere variations measured from radio atmospherics. Journal of Geophysical Research: Space Physics. 2010 Jan 1;115(10).

Published In

Journal of Geophysical Research: Space Physics

DOI

EISSN

2169-9402

Publication Date

January 1, 2010

Volume

115

Issue

10

Related Subject Headings

  • 5109 Space sciences
  • 5101 Astronomical sciences
  • 3706 Geophysics
  • 0401 Atmospheric Sciences
  • 0201 Astronomical and Space Sciences